SUMMARY 323 



(>. Compounds of Chlorine. — Sodium chlorideand Potassium 

 chloride, mentioned above. 



Hydrochloric acid, IIC1, is found in small amounts in the 

 gastric juice of the stomach where it aids in the enzyme 

 activity of digestion. 



7. Compounds, of Iodine are found in organic form in the 

 thyroid gland of man. 



8. Compounds of Silicon occur inorganic form in the hair. 

 234. Summary. — Animals, the highest product of the 



farm, are similar to plants in that they are living things that 

 reproduce themselves, and are composed largely of organic 

 matter. They differ from plants in many ways, one of them 

 being the manner of nutrition. Plants absorb inorganic 

 compounds in soluble form and from these compounds and 

 by their help the plant tissues are built up. Animals need 

 organic food already elaborated by plants, and are equipped 

 with the apparatus necessary to digest and render soluble 

 these foods before building up from them the animal 

 tissues. 



Animals need the same essential elements as do plants, 

 and in addition sodium, chlorine, iodine, silicon,. and fluorine. 

 Animals consist largely of water, although not to so great 

 an extent as plants, perhaps on the average not far from 

 60 per cent. There is a larger proportion of carbon to 

 oxygen in animals than in plants and more nitrogen. This 

 is because the dry matter of animals consists largely of 

 fats and proteins instead of carbohydrates and crude 

 fiber. 



Bones are the framework about which the other tissues 

 are grouped. They consist of about equal parts of mineral 

 matter, mostly tricalcium phosphate and calcium carbonate, 

 and of organic matter consisting of a protein called ossein. 

 Bones are hollow and permeated with marrow, which is 

 supposed to be the source of the red blood corpuscles. Muscle 

 tissue consists of bundles of fibers which have the power 

 of contraction and expansion, causing the various body 

 movements. Muscle is composed largely of proteins, the 

 principal one of which is called myosinogen, a liquid in the 

 living muscle, but changing to solid myosin in dead muscle. 



